/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated January 1, 2020. Replaces all prior versions.
 *
 * Copyright (c) 2013-2020, Esoteric Software LLC
 *
 * Integration of the Spine Runtimes into software or otherwise creating
 * derivative works of the Spine Runtimes is permitted under the terms and
 * conditions of Section 2 of the Spine Editor License Agreement:
 * http://esotericsoftware.com/spine-editor-license
 *
 * Otherwise, it is permitted to integrate the Spine Runtimes into software
 * or otherwise create derivative works of the Spine Runtimes (collectively,
 * "Products"), provided that each user of the Products must obtain their own
 * Spine Editor license and redistribution of the Products in any form must
 * include this license and copyright notice.
 *
 * THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL ESOTERIC SOFTWARE LLC BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES,
 * BUSINESS INTERRUPTION, OR LOSS OF USE, DATA, OR PROFITS) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THE SPINE RUNTIMES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

using System;

namespace Spine
{
    /// <summary>>An attachment with vertices that are transformed by one or more bones and can be deformed by a slot's
    /// <see cref="Slot.Deform"/>.</summary>
    public abstract class VertexAttachment : Attachment
    {
        static int nextID = 0;
        static readonly Object nextIdLock = new Object();

        internal readonly int id;
        internal int[] bones;
        internal float[] vertices;
        internal int worldVerticesLength;
        internal VertexAttachment deformAttachment;

        /// <summary>Gets a unique ID for this attachment.</summary>
        public int Id { get { return id; } }
        public int[] Bones { get { return bones; } set { bones = value; } }
        public float[] Vertices { get { return vertices; } set { vertices = value; } }
        public int WorldVerticesLength { get { return worldVerticesLength; } set { worldVerticesLength = value; } }
        ///<summary>Deform keys for the deform attachment are also applied to this attachment.
        /// May be null if no deform keys should be applied.</summary>
        public VertexAttachment DeformAttachment { get { return deformAttachment; } set { deformAttachment = value; } }

        public VertexAttachment(string name)
            : base(name)
        {

            deformAttachment = this;
            lock (VertexAttachment.nextIdLock)
            {
                id = (VertexAttachment.nextID++ & 65535) << 11;
            }
        }

        public void ComputeWorldVertices(Slot slot, float[] worldVertices)
        {
            ComputeWorldVertices(slot, 0, worldVerticesLength, worldVertices, 0);
        }

        /// <summary>
        /// Transforms the attachment's local <see cref="Vertices"/> to world coordinates. If the slot's <see cref="Slot.Deform"/> is
        /// not empty, it is used to deform the vertices.
        /// <para />
        /// See <a href="http://esotericsoftware.com/spine-runtime-skeletons#World-transforms">World transforms</a> in the Spine
        /// Runtimes Guide.
        /// </summary>
        /// <param name="start">The index of the first <see cref="Vertices"/> value to transform. Each vertex has 2 values, x and y.</param>
        /// <param name="count">The number of world vertex values to output. Must be less than or equal to <see cref="WorldVerticesLength"/> - start.</param>
        /// <param name="worldVertices">The output world vertices. Must have a length greater than or equal to <paramref name="offset"/> + <paramref name="count"/>.</param>
        /// <param name="offset">The <paramref name="worldVertices"/> index to begin writing values.</param>
        /// <param name="stride">The number of <paramref name="worldVertices"/> entries between the value pairs written.</param>
        public void ComputeWorldVertices(Slot slot, int start, int count, float[] worldVertices, int offset, int stride = 2)
        {
            count = offset + (count >> 1) * stride;
            Skeleton skeleton = slot.bone.skeleton;
            var deformArray = slot.deform;
            float[] vertices = this.vertices;
            int[] bones = this.bones;
            if (bones == null)
            {
                if (deformArray.Count > 0) vertices = deformArray.Items;
                Bone bone = slot.bone;
                float x = bone.worldX, y = bone.worldY;
                float a = bone.a, b = bone.b, c = bone.c, d = bone.d;
                for (int vv = start, w = offset; w < count; vv += 2, w += stride)
                {
                    float vx = vertices[vv], vy = vertices[vv + 1];
                    worldVertices[w] = vx * a + vy * b + x;
                    worldVertices[w + 1] = vx * c + vy * d + y;
                }
                return;
            }
            int v = 0, skip = 0;
            for (int i = 0; i < start; i += 2)
            {
                int n = bones[v];
                v += n + 1;
                skip += n;
            }
            var skeletonBones = skeleton.bones.Items;
            if (deformArray.Count == 0)
            {
                for (int w = offset, b = skip * 3; w < count; w += stride)
                {
                    float wx = 0, wy = 0;
                    int n = bones[v++];
                    n += v;
                    for (; v < n; v++, b += 3)
                    {
                        Bone bone = skeletonBones[bones[v]];
                        float vx = vertices[b], vy = vertices[b + 1], weight = vertices[b + 2];
                        wx += (vx * bone.a + vy * bone.b + bone.worldX) * weight;
                        wy += (vx * bone.c + vy * bone.d + bone.worldY) * weight;
                    }
                    worldVertices[w] = wx;
                    worldVertices[w + 1] = wy;
                }
            }
            else
            {
                float[] deform = deformArray.Items;
                for (int w = offset, b = skip * 3, f = skip << 1; w < count; w += stride)
                {
                    float wx = 0, wy = 0;
                    int n = bones[v++];
                    n += v;
                    for (; v < n; v++, b += 3, f += 2)
                    {
                        Bone bone = skeletonBones[bones[v]];
                        float vx = vertices[b] + deform[f], vy = vertices[b + 1] + deform[f + 1], weight = vertices[b + 2];
                        wx += (vx * bone.a + vy * bone.b + bone.worldX) * weight;
                        wy += (vx * bone.c + vy * bone.d + bone.worldY) * weight;
                    }
                    worldVertices[w] = wx;
                    worldVertices[w + 1] = wy;
                }
            }
        }

        ///<summary>Does not copy id (generated) or name (set on construction).</summary>
        internal void CopyTo(VertexAttachment attachment)
        {
            if (bones != null)
            {
                attachment.bones = new int[bones.Length];
                Array.Copy(bones, 0, attachment.bones, 0, bones.Length);
            }
            else
                attachment.bones = null;

            if (vertices != null)
            {
                attachment.vertices = new float[vertices.Length];
                Array.Copy(vertices, 0, attachment.vertices, 0, vertices.Length);
            }
            else
                attachment.vertices = null;

            attachment.worldVerticesLength = worldVerticesLength;
            attachment.deformAttachment = deformAttachment;
        }
    }
}
